The present invention relates to a technology which is effective when applied to an electronic component having an embedded high frequency power amplification circuit used in a wireless communication system such as a mobile phone to amplify a high frequency signal to be transmitted and output the amplified signal. More particularly, the present invention relates to a technology which is effective when used to detect an output power necessary for the feedback control of the output power.
In general, a transmitter output portion of a wireless communication apparatus (mobile communication apparatus) such as a mobile phone is provided with a high frequency power amplification circuit for amplifying a modulated signal to be transmitted. Since a conventional wireless communication apparatus controls the amplification factor of a high frequency power amplification circuit in accordance with a transmission level requested from a baseband circuit or a control circuit such as a microprocessor, it has been conventional practice to detect an output power of a high frequency power amplification circuit or an antenna and feedback it (see, e.g., Patent Document 1). Conventionally, the detection of the output power has been performed typically by using a coupler, a detection circuit, or the like and the detection circuit is constructed in most cases as a semiconductor integrated circuit distinct from the high frequency power amplification circuit.
A coupler is an element for detecting an output power via a capacitor formed between a discrete component or an output line (microstrip line) formed in an insulating substrate (module substrate) and a conductor disposed in parallel therewith, which is larger in size than the elements formed on a semiconductor chip. As for a directional coupler, it is described at, e.g., pages 191–193 of “Basics and applications of microwave circuits,” published by Sogo Denshi Publishing in Jul. 10, 1997. There is also a description on a ceramic multilayer lowpass filter for mobile communication and a directional coupler at pages 91–95 of the April 1999 issue of Electronic Materials, published by Kogyochosakai Publishing Co., Ltd.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-151310